During the last years, new classes of materials termed nanotubes have attracted considerable attention. The most well known nanotubes are the so-called carbon nanotubes (Iijima, S. Nature 1991, 254, 56) that exist either as single-walled carbon nanotubes, SWCNT, or as multi-walled carbon nanotubes, MWCNT. Numerous preparative routes to these materials have been patented (e.g. Smalley, R. E., U.S. Pat. No. 5,591,312; Smalley, R. E. at al., WO 98/39250; Jang, J. and Chung, S.-J., EP 1 046 613 A2; Smalley, R. E. et al., WO 00/17102; Cheng, H. et al., EP 1 061 044 A1 and EP 1 061 041 A1; Resasco, D. E. et al., WO 00/73205 A1; Kambe, N. and Bi, X., U.S. Pat. No. 6,045,769).
Carbon nanotubes have been shown to posses a wide range of physical properties that suggest that these materials could find use in a variety of technological applications. Particularly, the possibility of using carbon nanotubes as the building blocks in nanotechnology has recently been a major driving force for detailed studies of such materials. Carbon nanotubes are composed of graphite layers rolled up as cylinders with a diameter determined by the number of carbon atoms in the perimeter of the tube as shown in FIG. 1. The tubes can have closed ends. If there is only one cylindrical tube, the carbon nanotube material is termed single-walled (SWCNT). If more concentric cylindrical tubes are present (with a distance between the individual tubes of approximately 0.35 nm) the tubes are termed multi-walled (MWCNT). By high-resolution transmission electron microscopy (HRTEM) it is easily determined if a given sample contains either SWCNT or MWCNT. Obviously, to construct, for instance, electronic devices with the properties required for use in nanotechnological applications, it is desirable to have access also to nanotubes with a different chemical composition than carbon and thus with different physical and chemical properties. Consequently, much work has focused on the preparation of nanotubes of other materials. However, so far only a few materials have been isolated in the form of nanotubes, e.g., BN (Chopra, N. G. et al., Science 1995, 269, 966), BxCyNz (Stephan, O. et al., Science 1994, 266, 1683), WS2 (Tenne, R. et al., Nature 1992, 360, 444), MOS2 (Feldman, Y. et al., Science 1995, 267, 222 and Remskar, M. et al., Science 2001, 292, 479), NiCl2 (Hacohen, Y. R. et al., Nature 1998, 395, 336), NbS2 (Nath, M. and Rao, C. N. R., J. Am. Chem. Soc. 2001, 123, 4841 and Zhu, Y. et al., Chem. Commun. 2001, 2184), and Bi (Li, Y. et al., J. Am. Chem. Soc. 2001, 123, 9904).
A review article by R. Tenne (Progress in Inorganic Chemistry 2001, 50, 269) gives an overview of the area. A vanadium oxide nanotube material, which contains α,ω-diamines intercalated between the metal oxide layers, has also been described (Spahr, M. E. et al., Angew. Chem., Int. Ed. Engl. 1998, 37, 1263. and Krumeich, F. et al., J. Am. Chem. Soc. 1999, 121, 8324) and patented (Nesper, R. et al., Wo 01/30690 A2).
WO 00/66485 describes the synthesis of long nanotubes of transition metal chalcogenides. The method is based on the synthesis of nanoparticles of a transition metal oxide. The oxide particles are annealed with for instance H2S to obtain nanotubes. This method was used to produce nanotubes of wolfram sulphide, WS2. One limitation of this method is that not all transition metal oxides can be easily handled under the conditions stated in the method. That makes this method unsuitable for the preparation of for instance rhenium sulphide nanotube materials.
All the nanotube materials have layer structures in their ordinary polymophic modifications. NbS2, MOS2 and WS2 have closely related structures. Each individual layer in these materials consists of a metal atom layer sandwiched between two layers of sulphur atoms. The transition metal atoms are trigonal prismatically coordinated with sulphur atoms. So far, there have been no reports of nanotubes containing elements from group 7 of the Periodic Table (i.e. Mn, Tc, and Re).